Centrifugal compressor and geared centrifugal compressor

ABSTRACT

A centrifugal compressor includes a rotation shaft that extends along an axis; an impeller that includes a disk fixed to the rotation shaft and protruding outward in a radial direction, a plurality of blades provided in a surface facing one side in an axial direction of the disk to be separated from each other in a circumferential direction, and a cover covering the blades from the one side in the axial direction; and a casing that includes a facing inner peripheral surface facing an outer peripheral surface of the cover in the impeller and covers the impeller from an outside. The facing inner peripheral surface includes a cylindrical inner peripheral surface that extends along the axis and an enlarged inner peripheral surface that is connected to another side of the cylindrical inner peripheral surface in the axial direction and extends outward in the radial direction toward the other side.

TECHNICAL FIELD

The present invention relates to a centrifugal compressor, and particularly to a centrifugal impeller of a geared centrifugal compressor.

Priority is claimed on Japanese Patent Application No. 2015-026469, filed Feb. 13, 2015, the content of which is incorporated herein by reference.

BACKGROUND ART

In general, a centrifugal compressor includes an impeller which is provided in a rotation shaft and a casing which covers the impeller from the outside and defines a flow passage between the casing and the impeller. As the impeller rotates, an external fluid is suctioned through the flow path into the casing by the rotation of the impeller, and the fluid in a high-pressure state is discharged from an outlet of the casing by pressure being applied to the fluid while the fluid flows in the flow passage.

As an example of such a technology, a centrifugal compressor disclosed as below in Patent Literature 1 is known. In the centrifugal compressor disclosed in Patent Literature 1, a so-called closed impeller is employed. That is, this device includes a rotation shaft which rotates about an axis, a closed impeller (impeller) which includes a disk attached to the rotation shaft, a plurality of blades arranged on one surface of the disk, and a shroud provided at edges of the plurality of blades at one side in an axial direction, and a casing which covers the closed impeller from the outside. With the above-described configuration, a low-pressure fluid which flows from one side in the axial direction is compressed in accordance with the rotation of the impeller and is led from an outer discharge portion in a radial direction to the outside in the form of a high-pressure fluid.

Incidentally, in the above-described device, a labyrinth seal is generally provided in a space between the casing and the shroud and a space between the casing and the disk in order to prevent a reverse flow of the high-pressure fluid. In the device according to Patent Literature 1, a mouse labyrinth is provided between the shroud and the casing in the vicinity of an inlet of the closed impeller.

CITATION LIST Patent Literature

[Patent Literature 1]

Japanese Unexamined Patent Application, First Publication No. H04-203565

However, in the configuration disclosed in Patent Literature 1, there is also a possibility that the high-pressure fluid may flow reversely in a space from the discharge portion to the sealing portion (a space between the casing and the shroud). In such a case, a pressure which is generated by the high-pressure fluid is applied to both sides of the closed impeller in the axial direction. Accordingly, a compressing force, which is generated by the shroud and the disk, is applied to the blade. When a device is operated under atmospheric pressure or a device having a relatively low pressure difference is used, such a compressing force is small enough to be ignored. However, in a device having a high pressure difference, since the compressing force inevitably increases, there is a possibility that a durability of the blade may be influenced.

As a means for handling such a compressing force, for example, a method of increasing a thickness of the blade or increasing the number of the blades is considered. However, when such a technology is used, while a structural strength of the impeller is compensated, pressure loss of the fluid flowing in the impeller increases. That is, there is a possibility that compression efficiency of the centrifugal compressor is degraded.

SUMMARY OF INVENTION

One or more embodiments of the present invention provide a centrifugal compressor, in particular a geared centrifugal compressor, with sufficient durability and compression efficiency.

According to a first aspect of the present invention, a centrifugal compressor includes: a rotation shaft which extends along an axis; an impeller which includes a disk fixed to the rotation shaft and protruding outward in a radial direction, a plurality of blades provided in a surface facing one side in an axial direction of the disk to be separated from each other in a circumferential direction, and a cover covering the blades from the one side in the axial direction; and a casing which includes a facing inner peripheral surface facing an outer peripheral surface of the cover in the impeller and covers the impeller from an outside. The facing inner peripheral surface includes a cylindrical inner peripheral surface which extends along the axis and an enlarged inner peripheral surface which is connected to another side of the cylindrical inner peripheral surface in the axial direction and extends outward in the radial direction toward the other side. The centrifugal compressor further includes a sealing portion which seals a gap between the enlarged inner peripheral surface and the outer peripheral surface of the cover.

According to one or more embodiments, since the sealing portion seals a gap between the enlarged inner peripheral surface and the outer peripheral surface of the cover, it is possible to decrease a possibility that a high-pressure fluid reaches the cylindrical inner peripheral surface beyond the enlarged inner peripheral surface even when the high-pressure fluid flows reversely inside the casing. That is, it is possible to decrease an area of a region on which a pressure of the high-pressure fluid acts in the outer peripheral surface of the cover. Accordingly, it is possible to maintain desired compression efficiency without increasing a structural strength of the impeller.

According to a second aspect of the present invention, in the centrifugal compressor according to the first aspect, the sealing portion may include a plurality of sealing fins which are provided in the enlarged inner peripheral surface and extend in a direction from the enlarged inner peripheral surface toward the cover in the impeller.

According to one or more embodiments, a reverse flow of the high-pressure fluid between the enlarged inner peripheral surface and the outer peripheral surface of the cover can be suppressed by the plurality of sealing fins.

According to a third aspect of the present invention, in the centrifugal compressor according to the first aspect, the sealing portion may include a plurality of sealing fins which are provided in the enlarged inner peripheral surface to extend in a direction from the enlarged inner peripheral surface toward an inside in the radial direction of the axis and to be arranged in the axial direction, a protrusion portion which protrudes from the outer peripheral surface and includes a sealing surface extending parallel to the axis may be provided at a position corresponding to the sealing portion in the outer peripheral surface of the cover, and the sealing surface may face the plurality of sealing fins.

According to one or more embodiments, the plurality of sealing fins arranged in the axial direction and the sealing surface facing the sealing fins can suppress the reverse flow of the high-pressure fluid between the outer peripheral surface of the cover and the enlarged inner peripheral surface. In addition, it is possible to maintain a separation dimension between the sealing fin and the sealing surface even when a displacement of the rotation shaft in the axial direction occurs.

According to a fourth aspect of the present invention, in the centrifugal compressor according to the first aspect, the sealing portion may include a plurality of impeller side fins which are provided in a facing cover surface facing the enlarged inner peripheral surface in the cover and extend in a direction from the facing cover surface toward the enlarged inner peripheral surface.

According to one or more embodiments, the reverse flow of the high-pressure fluid between the facing cover surface and the enlarged inner peripheral surface can be sufficiently suppressed by the plurality of impeller side fins.

According to a fifth aspect of the present invention, the centrifugal compressor according to the fourth aspect may further include an abradable portion which is provided in the enlarged inner peripheral surface and is formed of a material abradable when brought into contact with front ends of the impeller side fins.

According to one or more embodiments, even when the front end of the impeller side fin is brought into contact with the enlarged inner peripheral surface due to a displacement caused by vibration with rotation of the impeller, a processing tolerance of the impeller, or a movement of the impeller in the axial direction, since the abradable portion having machinability is capable of being cut, it is possible to decrease a possibility of causing abrasion of the impeller side fin. Accordingly, it is possible to maintain a sealing property of the impeller side fin.

According to a sixth aspect of the present invention, in the centrifugal compressor according to any one of the first to fifth aspects, the sealing portion may be disposed in an area of 90% or less of a diameter dimension of the disk with reference to the axis.

According to one or more embodiments, when the sealing portion is provided in an area of 90% or less of the diameter dimension of the disk with reference to the axis, a space between the outer peripheral surface of the cover and the facing inner peripheral surface is divided into an outer radial area and an inner radial area with the sealing portion interposed therebetween. The high-pressure fluid flows in the outer radial area and a low-pressure fluid flows in the inner radial area. Accordingly, it is possible to optimize a pressure distribution applied to the outer peripheral surface of the cover by the high-pressure fluid.

According to a seventh aspect of the present invention, the centrifugal compressor according to any one of the first to sixth aspects may further include a back surface sealing portion which seals a gap between a surface of the disk facing the other side in the axial direction and the casing.

According to one or more embodiments, since the back surface sealing portion is provided, it is possible to decrease a possibility that the high-pressure fluid flows reversely through a gap between a surface of the disk facing the other side in the axial direction and the casing. Accordingly, it is possible to further decrease a compressing force applied to the impeller from both sides in the axial direction and also to decrease a thrust force applied to the rotation shaft in the axial direction.

According to an eighth aspect of the present invention, a geared centrifugal compressor may include: the centrifugal compressor according to any one of the first to seventh aspects; and a speed increasing transmission portion which includes a rotation driving shaft rotationally driven by an external driving source and an accommodation portion accommodating the rotation driving shaft and communicating with an inside of the casing and transmits a rotation of the rotation driving shaft to the rotation shaft of the centrifugal compressor.

According to one or more embodiments, it is possible to obtain the geared centrifugal compressor including the centrifugal compressor in which the possibility of the reverse flow of the high-pressure fluid inside the casing is decreased. Particularly, it is possible to sufficiently suppress a reverse flow of the high-pressure fluid directed from the inside of the casing of the centrifugal compressor toward the intake port of the impeller or the accommodation portion of the speed increasing transmission portion, and to reduce the compressing force from both sides of the impeller.

According to a ninth aspect of the present invention, in the eighth aspect, the geared centrifugal compressor may further include another centrifugal compressor which is disposed at an opposite side of the rotation shaft of the centrifugal compressor with the speed increasing transmission portion interposed therebetween and is plane symmetric with the centrifugal compressor with reference to a reference plane orthogonal to the axis.

According to one or more embodiments, the pair of centrifugal compressors having a plane symmetric shape with the reference plane interposed therebetween rotate. For this reason, even when the thrust force is generated in one centrifugal compressor toward one side of the rotation shaft in the axial direction, the same thrust force is generated in the other centrifugal compressor toward the other side in the axial direction. Accordingly, since these two thrust forces cancel each other, the thrust force of the rotation shaft in the axial direction can be reduced.

According to one or more embodiments of the centrifugal compressor and the geared centrifugal compressor, sufficient durability and compression efficiency can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a geared centrifugal compressor according to one or more embodiments of the present invention.

FIG. 2 is an enlarged view of a main part of a centrifugal compressor according to a first embodiment of the present invention.

FIG. 3 is an enlarged view of a sealing portion according to the first embodiment of the present invention.

FIG. 4 is an enlarged view of a main part of a centrifugal compressor according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of a main part of a centrifugal compressor according to a third embodiment of the present invention.

FIG. 6 is an enlarged view of a main part showing a modified example of the centrifugal compressor according to the third embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of a centrifugal compressor according to a fourth embodiment of the present invention.

FIG. 8 is an enlarged view of a main part of a centrifugal compressor according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the present invention will be described.

As shown in FIG. 1, a geared centrifugal compressor 100 according to the embodiment includes a speed increasing transmission portion 200 which includes a rotation driving shaft 102 driven by an external driving source and a pair of centrifugal compressors 1 which are disposed at both sides of the speed increasing transmission portion 200 to interpose the speed increasing transmission portion 200 therebetween. That is, the geared centrifugal compressor 100 is configured as a single-shaft two-stage compressor. Accordingly, a fluid which is compressed by one centrifugal compressor 1 (the first-stage centrifugal compressor 1) continuously flows into the other centrifugal compressor 1 (the second-stage centrifugal compressor 1). While the fluid flows through the second-stage centrifugal compressor, the fluid is further compressed to become a high-pressure fluid.

Further, in the description below, the single-shaft two-stage geared centrifugal compressor 100 will be exemplified. However, the embodiment of the geared centrifugal compressor 100 is not limited thereto, and a compressor having more compression stages and shafts may be employed.

More specifically, the geared centrifugal compressor 100 has a configuration in which the pair of centrifugal compressors 1 interposing the speed increasing transmission portion 200 are driven by the same rotation shaft 2. Further, the pair of centrifugal compressors 1 are formed to be approximately plane symmetric with reference to a reference plane CP, which is an imaginary plane orthogonal to an axis O, of the rotation shaft 2. In other words, one centrifugal compressor 1 is mirror-symmetric to the other centrifugal compressor 1.

However, dimensions of the parts of the pair of centrifugal compressors 1 may be different.

The speed increasing transmission portion 200 includes the rotation driving shaft 102, which includes a large-diameter gear 103 and is rotationally driven by an external driving source, and an accommodation portion 104, which accommodates a part of the rotation driving shaft 102 and the rotation shaft 2. The large-diameter gear 103 of the rotation driving shaft 102 is a disk-shaped gear extending in a plane orthogonal to an axis O of the rotation driving shaft 102.

When a high output and a high torque need to be achieved, a helical gear is suitably used as such a gear. In the large-diameter gear 103, a pitch of teeth or the like is appropriately set to be meshed with a pinion gear 3 provided in the rotation shaft 2 of the centrifugal compressor 1.

Further, a diameter dimension of the pinion gear 3 is set to be smaller than that of the large-diameter gear 103. Thus, the number of rotations of the rotation shaft 2 including the pinion gear 3 is larger than the number of rotations of the rotation driving shaft 102 including the large-diameter gear 103.

A bearing device 4 for rotatably supporting the rotation driving shaft 102 and the rotation shaft 2 is provided inside the accommodation portion 104 forming an outer shell of the speed increasing transmission portion 200. A device for supplying lubricating oil to the bearing device 4 may be separately provided.

With the above-described configuration, rotation of the rotation driving shaft 102 is transmitted to the rotation shaft 2 of the centrifugal compressor 1 through the large-diameter gear 103 and the pinion gear 3. Accordingly, the pair of centrifugal compressors 1 are operated.

Next, a configuration of the centrifugal compressor 1 according to the embodiment will be described with reference to FIG. 2. Further, as described above, since both of the pair of centrifugal compressors 1 in the geared centrifugal compressor 100 of the embodiment have the same configuration except that both of the compressors are plane symmetric, only one centrifugal compressor 1 will be described in the following description.

FIG. 2 is an enlarged view of a main part of the centrifugal compressor 1. As shown in the same drawing, the centrifugal compressor 1 includes the rotation shaft 2 which extends along the axis O, an impeller 5 which is provided in the rotation shaft 2, and a casing 6 which covers the impeller 5 from the outside.

The rotation shaft 2 is a rotation body which is formed in a columnar shape about the axis O and is rotated about the axis O by a rotational force transmitted from the speed increasing transmission portion 200.

The impeller 5 is an impeller which is provided at an intermediate position in a direction of the axis O of the rotation shaft 2. More specifically, the impeller 5 includes a substantially disk-shaped disk 7 which protrudes outward in a radial direction from an outer peripheral surface of the rotation shaft 2, a plurality of blades 8 which are provided at one surface of the disk 7 in a direction of the axis O, and a cover 9 which covers the plurality of blades 8 from one side in the direction of the axis O.

The disk 7 includes a disk support portion 71 which is fitted to a fitting groove 21 formed in the outer peripheral surface of the rotation shaft 2 and an annular disk body 72 which extends in a plate shape outward in a radial direction from the disk support portion 71.

The disk support portion 71 gradually increases in diameter from the inside to the outside in the radial direction from the one side toward the other side in the direction of the axis O. The disk body 72 protrudes outward in the radial direction from the outer peripheral surface at the other side in the direction of the axis O of the disk support portion 71. That is, the disk body 72 is formed in an annular plate shape.

A connection portion 73 between the disk support portion 71 and the disk body 72 is formed in a smooth curved surface shape. One surface in the direction of the axis O of the disk 7 with such a configuration is formed as a disk front surface 7A. Meanwhile, a surface opposite to the disk front surface 7A is smoothly formed as a disk back surface 7B. The disk back surface 7B extends to a surface substantially orthogonal to the axis O.

Each blade 8 is a blade member that has a thin plate shape and extends from the disk front surface 7A. Although not shown in detail, when viewed from the direction of the axis O, the blade 8 is curved toward one side as it goes from the inside toward the outer side in a radial direction of the disk 7.

Further, a height dimension of the blade 8, that is, a protrusion dimension from the disk front surface 7A, gradually decreases from the disk support portion 71 toward the disk body 72. In other words, an edge of the blade 8 facing the one side in the direction of the axis O, that is, an edge opposite to the disk 7, is curved so as to substantially correspond to the curved shapes of the disk support portion 71 and the disk body 72.

A plurality of the blades 8 with such a configuration are radially arranged on the disk front surface 7A about the axis O outward in the radial direction. That is, a circumferential gap is formed between a pair of adjacent blades 8.

Further, each edge of the plurality of blades 8 (the edge opposite to the disk 7) is provided with the cover 9 which is provided in an entire extending dimension. In other words, the plurality of blades 8 are covered by the cover 9 from the one side in the direction of the axis O. As described above, since the edge of the blade 8 is curved to correspond to the shape of the disk front surface 7A, the cover 9 is generally formed in a funnel shape.

Further, a separation dimension between the inner peripheral surface of the cover 9 and the disk front surface 7A gradually decreases from the inside toward the outside in the radial direction when viewed from the radial direction of the axis O. In one or more embodiments, the cover 9 is integrally formed by one member. An outer peripheral surface of the cover 9, that is, a surface facing the one side in the direction of the axis O, is formed as a facing cover surface 9A.

In the impeller 5 with such a configuration, an impeller flow passage 5F, which is surrounded by an inner peripheral surface of the cover 9 and the disk front surface 7A, is defined. Both sides of the impeller flow passage 5F in a circumferential direction are divided by a pair of adjacent blades 8. Since one side of the impeller flow passage 5F in the direction of the axis O is opened toward the one side in the direction of the axis O, an impeller intake port 51 is formed. Meanwhile, since an end opposite to the impeller intake port 51 in the impeller flow passage 5F is also opened in this way, an impeller discharge port 52 is formed.

The casing 6 forms a part of an outer shell of the centrifugal compressor 1 and covers the impeller 5 from the outside by allowing the inner peripheral surface to face the impeller. The casing 6 is provided with an intake flow passage 80 (an intake pipe 80) which communicates with the outside to intake air as a working fluid. As shown in FIG. 1, the intake pipe 80 is a cone-shaped member that gradually decreases in diameter from the one side toward the other side in the direction of the axis O. Air which enters through the intake flow passage 80 is led to the impeller flow passage 5F through the impeller intake port 51 inside the casing 6.

Further, a surface in the inner peripheral surface of the casing 6 facing the facing cover surface 9A in the impeller 5 with a gap therebetween is formed as a facing inner peripheral surface 6A. A surface which is positioned at the side opposite to the facing inner peripheral surface 6A with the impeller 5 interposed therebetween in the direction of the axis O is formed as a second facing inner peripheral surface 6B facing the disk back surface 7B with a gap interposed therebetween.

An area which is surrounded by the facing inner peripheral surface 6A and the second facing inner peripheral surface 6B is provided with a diffuser 6E which is opened toward the outside from an outer end thereof in the radial direction. The diffuser 6E communicates with an exhaust flow passage 90 (an exhaust flow passage 90). As shown in FIG. 1, the exhaust flow passage 90 is a pipe body which extends in a spiral shape while surrounding the intake pipe 80 from the outer peripheral side. High-pressure air is supplied to an external device (not shown) through the exhaust flow passage 90 and is used for various purposes.

Further, the facing inner peripheral surface 6A includes a cylindrical inner peripheral surface 61A which is formed in a cylindrical shape and substantially extends along the axis O, and an enlarged inner peripheral surface 62A which is connected to the other end of the cylindrical inner peripheral surface 61A in the direction of the axis O and similarly extends outward in the radial direction toward the other side.

In addition, the second facing inner peripheral surface 6B in the inner peripheral surface of the casing 6 extends in a plane shape substantially parallel to the outer peripheral surface of the rotation shaft 2. A radial gap is formed between the second facing inner peripheral surface 6B and the outer peripheral surface of the rotation shaft 2. The gap communicates with the inside of the accommodation portion 104 in the speed increasing transmission portion 200 through a shaft sealing portion 2S.

The shaft sealing portion 2S is a sealing member that is provided in an area directly facing the rotation shaft 2 in the inner peripheral surface of the casing 6. The shaft sealing portion 2S is provided to reduce leakage of air toward the accommodation portion 104 of the speed increasing transmission portion 200.

A sealing portion 10 is provided between the casing 6 and the impeller 5 which are formed as described above. More specifically, the sealing portion 10 according to the embodiment is provided on the enlarged inner peripheral surface 62A in the facing inner peripheral surface 6A of the casing 6. Particularly, in one or more embodiments, a separation dimension D2 in the radial direction from the axis O to the sealing portion 10 may be 90% or less of a diameter dimension D1 of the disk as indicated by a dimension line of FIG. 2 upon providing the sealing portion 10 on the enlarged inner peripheral surface 62A.

Next, a detailed configuration of the sealing portion 10 will be described on the basis of FIG. 3. As shown in FIG. 3, the sealing portion 10 includes a base portion 11 which is formed in a substantially plate shape and extends along the enlarged inner peripheral surface 62A inside the casing 6, and a plurality of sealing fins 12 which extend from the base portion 11 toward the cover 9 of the impeller 5.

Since the sealing fin 12 is formed to be gradually tapered from a side which contacts with the base portion 11 toward a front end thereof, the sealing fin is formed in a wedge shape in a cross-sectional view. Further, in the embodiment, the plurality of sealing fins 12 are arranged on the surface of the base portion 11 at intervals. However, the shape of the sealing fin 12 is not limited thereto and, for example, the sealing fins 12 may be arranged in close contact with each other without spacing.

The front end of the sealing fin 12 with such a configuration forms a slight gap with respect to the facing cover surface 9A of the facing impeller 5. Since the gap is formed, a possibility of the rotating impeller 5 contacting the sealing fin 12 decreases, and thus sufficient sealing performance can be exhibited.

Operations of the centrifugal compressor 1 and the geared centrifugal compressor 100 with the above-described configuration will be described.

First, the rotation driving shaft 102 of the speed increasing transmission portion 200 is rotationally driven by an external driving source. As such a driving source, for example, an electric motor or a steam turbine is appropriately selected according to designs and specifications. That is, when an output shaft of the electric motor or the steam turbine is connected to the rotation driving shaft 102, rotation thereof can be transmitted to the rotation driving shaft 102.

As the rotation driving shaft 102 rotates, the large-diameter gear 103 provided on the rotation driving shaft 102 also rotates. The large-diameter gear 103 meshes with the pinion gear 3 provided on the rotation shaft 2 of the centrifugal compressor 1. Accordingly, the rotation of the rotation driving shaft 102 is transmitted to the rotation shaft 2 of the centrifugal compressor 1, and the rotation shaft 2 starts to rotate in a direction opposite to a rotation direction of the rotation driving shaft 102.

Since the rotation shaft 2 rotates, the pair of centrifugal compressors 1 which are provided adjacent to the speed increasing transmission portion 200 are driven. First, the impeller 5 rotates inside the casing 6 in accordance with the rotation of the rotation shaft 2. As described above, the impeller intake port 51 which intakes air as a working fluid is provided at one side of the impeller 5 in the direction of the axis O. In accordance with an increase in the number of rotations of the impeller 5, air is taken into the impeller flow passage 5F through the impeller intake port 51.

The air which is taken into the impeller flow passage 5F receives torque while flowing toward the impeller discharge port 52 inside the impeller flow passage 5F due to the rotation of the impeller 5 and is compressed by the impeller flow passage 5F to become high-pressure air. The high-pressure air passes through the impeller discharge port 52 of the impeller flow passage 5F and flows toward the diffuser 6E. The high-pressure air which flows into the diffuser 6E is led to the outside through the exhaust flow passage 90 provided in the casing 6.

Here, as described above, while the high-pressure air exists in the vicinity of the impeller discharge port 52 and the diffuser 6E, uncompressed air flows in the gap formed by the facing inner peripheral surface 6A of the casing 6 and the outer peripheral surface (the facing cover surface 9A) of the cover 9. Thus, there is a possibility in which the high-pressure air flows into the gap due to a pressure difference.

However, as described above, in the centrifugal compressor 1 according to the embodiment, since the facing inner peripheral surface 6A is provided with the plurality of sealing fins 12 serving as the sealing portion 10, the flow of the high-pressure air can be sealed. That is, it is possible to decrease a possibility that the high-pressure air flows reversely toward a low-pressure area.

Particularly, in the embodiment, the sealing portion 10 is provided on the enlarged inner peripheral surface 62A of the facing inner peripheral surface 6A. Accordingly, it is possible to decrease a possibility that the high-pressure air flows over the sealing portion 10 to flow into the cylindrical inner peripheral surface 61A.

Here, when the sealing portion 10 is provided on the cylindrical inner peripheral surface 61A differently from the configuration of the embodiment, the high-pressure air reaches an area including the cylindrical inner peripheral surface 61A. In this case, pressure which is generated by the high-pressure air is exhibited in the impeller 5 through the outer peripheral surface of the cover 9. Further, since the high-pressure air can flow into the gap between the disk back surface 7B and the second facing inner peripheral surface 6B of the casing 6, a compressing force F1 which is generated by the high-pressure air is applied to both sides of the impeller 5 in the direction of the axis O.

However, in the centrifugal compressor 1 according to the embodiment, as described above, the sealing portion 10 is provided on the facing inner peripheral surface 6A, that is, the enlarged inner peripheral surface 62A. Accordingly, it is possible to decrease a size of an area into which the high-pressure air can be flown in an entire area of the gap. That is, it is possible to decrease an area of a region that receives a pressure generated by the high-pressure air in the outer peripheral surface of the cover 9. Accordingly, it is possible to maintain desired compression efficiency without increasing the structural strength of the impeller 5.

Meanwhile, for example, when a thickness of the blade 8 is increased or the number of the blades 8 per impeller 5 is increases in order to improve the structural strength of the impeller 5, pressure loss of the working fluid flowing inside the impeller 5 increases. That is, the compression efficiency of the centrifugal compressor 1 is degraded. However, in the centrifugal compressor 1 according to the embodiment, it is possible to obtain the above-described operational effect while maintaining the structural strength of the impeller 5. Thus, it is possible to sufficiently ensure the compression efficiency of the centrifugal compressor 1.

Further, as described above, when the sealing portion 10 is provided in an area of 90% or less of the diameter dimension D1 of the disk with reference to the axis O, a space between the outer peripheral surface of the cover 9 and the facing inner peripheral surface 6A is divided into an outer radial area and an inner radial area with the sealing portion 10 interposed therebetween. The high-pressure fluid flows in the outer radial area and the low-pressure fluid flows in the inner radial area. Accordingly, it is possible to optimize a pressure distribution applied to the outer peripheral surface of the cover 9 by the high-pressure fluid.

Incidentally, when the sealing portion 10 is provided on the enlarged inner peripheral surface 62A as described above, while a pressure applied to the outer peripheral surface of the cover 9 decreases, a high pressure between the second facing inner peripheral surface 6B and the disk back surface 7B is maintained. Due to the pressure difference, a thrust force F2 is generated in the rotation shaft 2 and the impeller 5 in a direction from the other side toward the one side in the direction of the axis O (that is, the direction from the disk 7 toward the cover 9 along the axis O).

However, as described above, the geared centrifugal compressor 100 according to the embodiment includes the pair of centrifugal compressors 1 which are plane symmetric and the speed increasing transmission portion 200 (the reference plane CP) is interposed therebetween. Thus, when the same sealing portion 10 is provided in the pair of centrifugal compressors 1, thrust forces F2 in the centrifugal compressors 1 are exerted along the axis O in a separation direction. Accordingly, since the thrust forces F2 cancel each other, a thrust load applied to the bearing device 4 can be suppressed.

The first embodiment of the present invention has been described with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiment are not particularly limited to the scope of the present invention unless otherwise specified, and various modifications can be made thereto.

For example, in the first embodiment, the geared centrifugal compressor 100 having a so-called single-shaft two-stage configuration has been exemplified. However, the shape of the geared centrifugal compressor 100 is not limited thereto and more shafts and more stages may be provided, such as two shafts and four stages, in accordance with designs or specifications. In any configuration, it is possible to obtain the same operational effect as the description in the above-described embodiment in the centrifugal compressor 1 in each stage.

Further, in the above-described embodiment, an example in which the plurality of sealing fins 12 are used as the sealing portion 10 has been described. However, the shape of the sealing portion 10 is not limited thereto and any configuration may be employed as long as a fluid in the flow passage is sealed.

In addition, even when the plurality of sealing fins 12 are provided, the sealing fins 12 may be formed to have different shapes and dimensions. Specifically, dimensions of the sealing fin 12 may be formed to increase or decrease from one side toward the other side in the plurality of sealing fins 12.

Second Embodiment

Next, a second embodiment of the present invention will be described with reference to FIG. 4. Further, the same reference numerals will be given to the same components and members as those of the first embodiment, and detailed descriptions thereof will be omitted.

As shown in FIG. 4, in the centrifugal compressor 1 according to the embodiment, a shape of the sealing portion 10 is different from that of the first embodiment. That is, the sealing portion 10 of the embodiment is formed by a plurality of impeller side fins 121 which are provided on an outer peripheral surface of the cover 9 of the impeller 5. Each of the impeller side fins 121 is formed in a thin plate shape extending toward the facing inner peripheral surface 6A (the enlarged inner peripheral surface 62A) separated from the outer peripheral surface of the cover 9 with a gap interposed therebetween. Here, in the example of FIG. 4, the impeller side fin 121 is formed without interposing the base portion 11 described in the first embodiment. Further, desirably, the impeller side fin 121 is integrally formed in the cover 9.

Similarly to the first embodiment, it is desirable to set installation positions of the impeller side fins 121 so that the separation dimension D2 from the axis O to the impeller side fin 121 in the radial direction is 90% or less of the diameter dimension D1 of the disk.

Even in the above-described configuration, reverse flow of a high-pressure fluid between the enlarged inner peripheral surface 62A and the outer peripheral surface of the cover 9 can be sufficiently suppressed by the plurality of impeller side fins 121. Accordingly, it is possible to ensure sufficient compression efficiency without specially compensating the structural strength of the centrifugal compressor 1.

Third Embodiment

Next, a third embodiment of the present invention will be described with reference to FIG. 5. Further, the same reference numerals will be given to the same components and members as those of the first embodiment, and detailed descriptions thereof will be omitted.

As shown in FIG. 5, in the centrifugal compressor 1 according to the embodiment, a back surface sealing portion 101 is provided between the second facing inner peripheral surface 6B of an inner peripheral surface of the casing 6 and the disk back surface 7B in addition to the sealing portion 10 of the first embodiment. Similarly to the configuration shown in FIG. 3, the back surface sealing portion 101 includes the base portion 11 which is provided in the second facing inner peripheral surface 6B and the plurality of sealing fins 12 which are provided in the base portion 11.

As described above, there is a possibility that the high-pressure air flows reversely from the vicinity of the diffuser 6E into the gap formed between the second facing inner peripheral surface 6B and the disk back surface 7B. Particularly, in the geared centrifugal compressor 100, the accommodation portion 104 of the speed increasing transmission portion 200 communicates with the inside of the casing 6. In this case, a possibility that the high-pressure air flows reversely toward the accommodation portion 104 having a relatively low pressure further increases.

However, when the back surface sealing portion 101 is provided like in the embodiment, it is possible to seal the flow of the high-pressure air which flows reversely. Accordingly, it is possible to reduce a pressure applied from the disk back surface 7B to the impeller 5 by the high-pressure air.

Thus, since it is possible to obtain the same operational effect as those of the above-described embodiments while maintaining the structural strength of the impeller 5, it is possible to sufficiently ensure the compression efficiency of the compressor.

Additionally, in the embodiment, as the back surface sealing portion, a configuration which includes the base portion 11 provided in the second facing inner peripheral surface 6B and the plurality of sealing fins 12 provided in the base portion 11 has been exemplified. However, the shape of the back surface sealing portion 101 is not limited thereto. For example, as shown in FIG. 6, the plurality of sealing fins 12 may be integrally provided on the disk back surface 7B of the impeller 5 to form the back surface sealing portion 101.

According to such a configuration, the reverse flow of the high-pressure fluid can be sufficiently suppressed by the plurality of sealing fins 12. Accordingly, it is possible to ensure sufficient compression efficiency without specially compensating the structural strength of the centrifugal compressor 1.

Further, when the fins are integrally formed in the impeller 5 (the disk back surface 7B) as described above, it is possible to reduce the number of steps and costs necessary for manufacturing the impeller 5 and the casing 6.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described with reference to FIG. 7. Further, the same reference numerals will be given to the same components and members as those of the first embodiment, and detailed descriptions thereof will be omitted.

As shown in FIG. 7, in the centrifugal compressor 1 according to the embodiment, a shape of the sealing portion 10 is different from those of the above-described embodiments. That is, in the centrifugal compressor 1 according to the embodiment, an abradable portion 70 is provided on the facing inner peripheral surface 6A facing the impeller side fin 121 in addition to the sealing portion 10 of the second embodiment, in other words, on the plurality of impeller side fins 121 provided on the outer peripheral surface of the cover 9.

The abradable portion 70 is a material having good machinability obtained by being compacted and molded, for example, a fine aluminum powder. That is, the abradable portion 70 has a property such that the abradable portion is easily cut when brought into contact with other members and does not influence abrasion of the contacted member.

According to such a configuration, since the abradable portion 70 having machinability is cut even when a front end of the impeller side fin 121 is brought into contact with the enlarged inner peripheral surface 62A due to a displacement of the impeller 5 caused by vibration with a rotation, a processing tolerance of the impeller 5, and a movement of the impeller 5 in the direction of the axis O, a possibility of causing abrasion of the impeller side fin 121 can be reduced. Accordingly, it is possible to maintain a sealing property due to the impeller side fin 121.

Additionally, in the embodiment, an example using a material, which is compacted fine aluminum powder, as the abradable portion 70 has been described. However, the material and the shape of the abradable portion 70 are not limited thereto and any material may be used as long as satisfactory machinability is ensured. That is, the shape is not uniquely limited as long as the shape exhibits hardness lower than a material of the impeller 5 (the cover 9) and has machinability.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described with reference to FIG. 8. Further, the same reference numerals will be given to the same components and members as those of the first embodiment, and detailed descriptions thereof will be omitted.

As shown in FIG. 8, in the centrifugal compressor 1 according to the embodiment, an extension direction of the sealing fin 12 in the sealing portion 10 is mainly different from those of the above-described embodiments. That is, in the embodiment, the sealing portion 10 is provided inside an accommodation groove 62B and all sealing fins 12 extend inward in the radial direction of the axis O.

Further, in the embodiment, a protrusion portion 9B is formed at a position corresponding to the sealing portion 10 on the facing cover surface 9A of the impeller 5. The protrusion portion 9B protrudes from the facing cover surface 9A substantially toward one side in the direction of the axis O as shown in FIG. 8. The protrusion portion 9B has a substantially triangular shape which extends in a normal direction of a bottom side corresponding to a part of the facing cover surface 9A.

Particularly, a sealing surface 9C which is a surface facing the outside in the radial direction of the axis O among two surfaces forming a cross-section is formed to be substantially parallel to an arrangement direction of the sealing fins 12 in the sealing portion 10. In other words, the sealing surface 9C forms a plane which is substantially parallel to the axis O. Further, a part of the protrusion portion 9B including the sealing surface 9C extends to the inside of the accommodation groove 62B. Accordingly, front ends of the plurality of sealing fins 12 face the sealing surface 9C to seal a gap between the facing cover surface 9A and the facing inner peripheral surface 6A.

According to the above-described configuration, since the sealing fins 12 of the sealing portion 10 are arranged in the direction of the axis O, it is possible to maintain a separation dimension between the front end of the sealing fin 12 and the sealing surface 9C facing the front end even when the rotation shaft 2 is displaced in the direction of the axis O. Thus, it is possible to seal a gap between the facing inner peripheral surface 6A and the facing cover surface 9A regardless of an operation state of the centrifugal compressor 1.

INDUSTRIAL APPLICABILITY

According one or more embodiments of the above-described centrifugal compressor and the geared centrifugal compressor, sufficient durability and compression efficiency can be realized.

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.

REFERENCE SIGNS LIST

1 Centrifugal compressor

2 Rotation shaft

2S Shaft sealing portion

3 Pinion gear

4 Bearing device

5 Impeller

6 Casing

7 Disk

8 Blade

9 Cover

10 Sealing portion

11 Base portion

12 Sealing fin

21 Fitting groove

51 Impeller intake port

52 Impeller discharge port

5F Impeller flow passage

6A Facing inner peripheral surface

6B Second facing inner peripheral surface

6E Diffuser

7A Disk front surface

7B Disk back surface

9A Facing cover surface

9B Protrusion portion

9C Sealing surface

61A Cylindrical inner peripheral surface

62A Enlarged inner peripheral surface

62B Accommodation groove

70 Abradable portion

71 Disk support portion

72 Disk body

73 Connection portion

80 Intake flow passage

80 Intake pipe

90 Exhaust flow passage

100 Geared centrifugal compressor

101 Speed increasing transmission portion

200 Back surface sealing portion

102 Rotation driving shaft

103 Large-diameter gear

104 Accommodation portion

121 Impeller side fin

CP Reference plane

D1 Diameter dimension of disk

D2 Separation dimension of radial direction

F1 Compressing force

F2 Thrust force

O Axis 

1. A centrifugal compressor comprising: a rotation shaft that extends along an axis; an impeller that includes: a disk fixed to the rotation shaft and protruding outward in a radial direction; a plurality of blades provided in a surface facing one side in an axial direction of the disk to be separated from each other in a circumferential direction and a cover covering the blades from the one side in the axial direction; and a casing that includes a facing inner peripheral surface facing an outer peripheral surface of the cover in the impeller and covers the impeller from an outside, wherein the facing inner peripheral surface includes: a cylindrical inner peripheral surface that extends along the axis; and an enlarged inner peripheral surface that is connected to another side of the cylindrical inner peripheral surface in the axial direction and extends outward in the radial direction toward the other side, wherein the centrifugal compressor further comprises a sealing portion that seals a gap between the enlarged inner peripheral surface and the outer peripheral surface of the cover, and wherein the sealing portion is disposed in an area of 90% or less of a diameter dimension of the disk with reference to the axis.
 2. The centrifugal compressor according to claim 1, wherein the sealing portion includes a plurality of sealing fins that are provided in the enlarged inner peripheral surface and extend in a direction from the enlarged inner peripheral surface toward the outer peripheral surface of the cover in the impeller.
 3. The centrifugal compressor according to claim 1, wherein the sealing portion includes a plurality of sealing fins that are provided in the enlarged inner peripheral surface to extend in a direction from the enlarged inner peripheral surface toward an inside in the radial direction of the axis and to be arranged in the axial direction, wherein a protrusion portion that protrudes from the outer peripheral surface of the cover and includes a sealing surface extending parallel to the axis is provided at a position corresponding to the sealing portion in the outer peripheral surface of the cover, and wherein the sealing surface faces the plurality of sealing fins.
 4. The centrifugal compressor according to claim 1, wherein the sealing portion includes a plurality of impeller side fins that are provided in a facing cover surface facing the enlarged inner peripheral surface in the cover and extend in a direction from the facing cover surface toward the enlarged inner peripheral surface.
 5. The centrifugal compressor according to claim 4, further comprising: an abradable portion that is provided in the enlarged inner peripheral surface and is formed of a material abradable when brought into contact with front ends of the impeller side fins.
 6. (canceled)
 7. The centrifugal compressor according to claim 1, further comprising: a back surface sealing portion that seals a gap between a surface of the disk facing the other side in the axial direction and the casing.
 8. A geared centrifugal compressor comprising: the centrifugal compressor according to claim 1; and a speed increasing transmission portion that includes a rotation driving shaft rotationally driven by an external driving source and an accommodation portion accommodating the rotation driving shaft and communicating with an inside of the casing, and transmits a rotation of the rotation driving shaft to the rotation shaft of the centrifugal compressor.
 9. The geared centrifugal compressor according to claim 8, further comprising: another centrifugal compressor that is disposed at an opposite side of the rotation shaft of the centrifugal compressor with the speed increasing transmission portion interposed therebetween, and is plane symmetric with the centrifugal compressor with reference to a reference plane orthogonal to the axis. 